72 report — 1865. 



surfaces and up ascending slopes ; and confronted with accurate notions and exact 

 maps of definite tracts selected for study. Pie then described the special phenomena 

 which had been observed by Mr. Lee and himself, on a swelling ground at the foot 

 of the Corner Glacier. In this case he showed that beautiful striation and polish 

 were traceable on broad flat surfaces (protected by a shed) 150 feet above the actual 

 bed of the glacier, and about ICO yards from its base. He showed that this was 

 quite consistent with the known physical constitution of ice, and the slopes of the 

 ground, steep as these are. It is quite clear that on such ascending slopes the up- 

 ward movement of the ice, by pressure from the higher parts of the glacier, is a 

 real and necessary result. That the glacier formerly extended much beyond its 

 present limits is well proved by other facts. The author next described the pheno- 

 mena of glacial movement in Wastdale, and the features of Wastwater, a deep 

 straight lake, three miles long. In these can be shown the reality of partial move- 

 ments of ice in the valley, but from the great length of the lower, almost level 

 tracts of ground, and the shortness of the upper snow slopes in ancient days, he 

 concluded that effective pressure could not be continued through the length of 

 Wastdale. Among other reasons for this, he instanced the fact that under the pres- 

 sure equivalent to 1000 or 1500 vertical feet of ice, that substance would lose its 

 solidity. He also showed by a study of the relative grinding force of the icy weight 

 under different conditions of deptli and inclination, that if such pressure could be 

 communicated, it would not be effective in excavating the lake. It would not tend 

 to make a hollow such as a lake would till, nor to deepen such a hollow if previously 

 placed in its path in Wastdale. On the whole, he concluded that for a satisfactory 

 explanation of the full wearing and excavating effect of ice in valleys and lakes it 

 would be necessary always to treat each case as a special problem, by no means 

 purely geological, but including important and quite practicable mechanical deter- 

 minations. 



On the Geology of Coalhvoolc Dale. B>j the Rev. W. Pueton. 



Just where the valley of the Severn contracts towards the narrow gorge through 

 which it passes the limestone ridge of Wenlock Edge, it is joined by the lateral 

 valley of Coalbrook Dale, running down from the high table-land which forms the 

 chief part of the Shropshire coal-field. The Dale, which is for the most part 

 scooped out of the Wenlock shale, is joined about midway down by the hollow 

 through which the railway ascends to Lightmoor, and which is excavated in the 

 Lower coal-measures here faulted down; and is flanked at its entrance into the 

 Severn valley by the Mound called Strethill on the north, and by Lincoln Hill on 

 the south. At Strethill, we find the mass of glacial drift, 200 feet high above the 

 Severn, which formed the subject of Mr. G. Maw's paper read before the Geologi- 

 cal Society, and printed in their Quarterly Journal for May 1864; and which has 

 served to prove that at one time during the glacial epoch Wenlock Edge was the 

 coast-line of the Irish Sea, and the Severn valley a marine strait. At Lincoln Hill 

 the Wenlock limestone, which rests at a high angle on the shale, is now worked in 

 a series of extensive caverns ; but in the old surface workings we may still see the 

 cavities whence the Ball-stone has been extracted, as described by Sir Roderick 

 Murchison in his ' Siluria.' And there is also exposed a highly interesting sec- 

 tion, showing the Lower coal-measures resting- immediately on the Wenlock lime- 

 stone. The lowest seam of coal, the " Lancashire Ladies," and the " Crawstone " 

 ironstone are visible. A walk along the south side of the Dale, about a mile, 

 brings us to Lightmoor Wood, in a quarry in which the fossil tree was found which 

 was figured some time since in the ' Illustrated London News.' In this quarry 

 we again met with the Crawstone ironstone, and are able to trace the series ot 

 strata upwards to the "Little Flint" coal and "Clod" coal; while in the Light-, 

 moor railway-cutting close at hand, we have exposed no less than six different 

 seams of coal capped by the " Pennystone " ironstone. In a brick-field about 100 

 yards to the north still higher strata are exposed ; and thus in a walk of little more 

 than a mile, we may see in open sections the whole of the Lower coal-measures, 

 and a portion of the Pppcr. It is to these sections I wish to direct the attention 

 of those Members of the Association who are about to visit Coalbrook Dale. For 

 a detailed account of the Shropshire coal-field, the estuarine character of its strata, 



